The crimes of Bigamy and Marrying a Bigamist in Illinois are defined by 720 ILCS 5/11-45 as follows:
(720 ILCS 5/11-45) (was 720 ILCS 5/11-12)
Sec. 11-45. Bigamy and Marrying a bigamist.
(a) Bigamy. A person commits bigamy when that person has a husband or wife and subsequently knowingly marries another.
(a-5) Marrying a bigamist. An unmarried person commits marrying a bigamist when that person knowingly marries another under circumstances known to him or her which would render the other person guilty of bigamy under the laws of this State.
(b) It shall be an affirmative defense to bigamy and marrying a bigamist that:
(1) The prior marriage was dissolved or declared invalid; or
(2) The accused reasonably believed the prior spouse to be dead; or
(3) The prior spouse had been continually absent for a period of 5 years during which time the accused did not know the prior spouse to be alive; or
(4) The accused reasonably believed that he or she or the person he or she marries was legally eligible to be married.
Bigamy is a Class 4 felony. Marrying a bigamist is a Class A misdemeanor.
Bigamy, as a Class 4 felony in Illinois, can result in a prison sentence of 1-3 years. The crime of marrying a bigamist is a Class A misdemeanor, which can result in a jail sentence of up to 1 year. Bigamy can also, of course, have a significant impact upon a pending divorce case in Illinois.